Automobiles are increasingly reliant on electronic controls and engine management systems. As a result of these controls and systems, modem automobiles are much more dependable than prior autos, which instead used more vulnerable mechanical systems. Although the hardware embodying the electronic controls and systems is rather dependable, the failure of the means for directly or indirectly bringing electrical current to such hardware continues to be a rare but, nevertheless, significant source of automotive breakdowns. An automotive breakdown, especially in a deserted area or on a very busy high-speed road, is obviously a safety hazard to the automobile and its passengers.
One specific type of failure in prior art means can lead to an even more hazardous condition than automotive breakdown. This failure occurs at the junction wherein a fusible link is connected to an electrical center through a stud mounting. Typically a nut and threaded stud combination fixes the fusible link to the electrical center. However, due to incorrect torquing force applied to the nut, a number of the junctions will ultimately fail. When the fusible link becomes loosened from the stud mounting the resistance is increased in these areas, which results in increased temperatures. Under certain conditions these temperatures can reach sufficiently high levels to split the insulation on the fusible links, initiating an engine compartment fire that can quickly destroy the automobile and endanger its occupants.
A similar type of failure occurs at the connection or junction between the fusible link and a current-carrying cable. Notwithstanding the best efforts of electrical circuit designers and the highest quality connecting techniques, a highly predictable number of such junctions will ultimately fail. Similar to above, the failure results when the junctions loosen, causing a high resistance between the fusible link and cable. The increased resistance leads to high temperatures in the regions. Under certain conditions, these temperatures can reach sufficiently high levels to burn the insulation covering the cables, initiating a dangerous fire.
U.S. Pat. No. 5,591,366 issued to Schmidt et al. discloses a series of protective coverings over a heating wire connected to a power wire. The heating wire is connected in series to an electrical pin which directly joined to a fuse wire. The fuse wire is then joined to the power wire. Two opposing metal caps are bonded on their inner surfaces to a ceramic tube to form a hermetically sealed shell surrounding the junctions between the fuse wire and pin, and between the fuse wire and power wire. Then, a heat shrinkable tubing is used to grip the caps and ceramic tubing, encasing the fuse area.
Like other prior art devices, the disclosure of U.S. Pat. No. 5,591,366 does not solve the problem of protecting failure at the junctions of the fusible link due to force applied to the cable assembly.
In addition to the excess heat generated due to failures at the junctions of the fusible link and the cable, excess heat is often generated by the fusible link itself causing a failure of the insulative housing as well.
Fusible links are commonly used to interrupt current in electrical circuits. These fusible links may take the form of metal wire that melts upon current overload occurring over pre-designated spans of time. The fusible links may also take the form of thin, fusible pieces of metal that form a bridge between terminals or terminal extensions, such as the thin fusible link that appears in the ATO.RTM., MINI.RTM. or MAXI.RTM. fuses manufactured and sold by the assignee of the present invention.
Prior art wire link devices are commonly made of copper or tin-plated copper, and are generally insulated with a polymeric or rubber-based insulating cover. Such insulated copper wire links have been generally satisfactory for their intended purposes, but have certain deficiencies that make them less than ideal. For example, copper wire links have very high melting temperatures, i.e., approximately 1083.degree. C. The insulating cover cannot withstand such temperatures and, under certain excessive current conditions, will melt, split, bum or separate from the wire long before the copper wire link melts. Accordingly, there is a perceived need for a fusible link to replace copper wire links in such applications, which would melt at temperatures lower than the deformation or burning temperatures of the insulation, even under conditions which could cause insulation deformation or burning with copper links.
Accordingly, a fusible link and cable assembly in accordance with the present invention eliminates the drawbacks of the prior art devices described above.